It is well known, that the internal quality of eggs is diminished with time. The loss in quality attributes of the albumen and yoke is a function of temperature and movement of carbon dioxide through the shell. Low temperatures decrease the rate of loss in Haugh units—a standard measure of interior egg quality—and thus it is recommended that eggs be stored at temperatures close to the freezing point, a procedure which, as a practical matter, is not always feasible. To reduce rate of carbon dioxide (and moisture) loss various shell treatments have been utilized, such as spraying oil on the eggs.
Freshness is one of the most important parameters in indicating the internal quality of an egg. The moment an egg is laid, it is starting to become stale. When the housekeeper cracks an egg, he/she is expecting to find a series of visual clues indicating how fresh the egg is. The watery status of the white and the consistency of the vitelline membrane (yolk membrane) are two parameters to indicate the freshness of an egg. This is also important for the egg and the bakery industry, because a stale egg will fail to rise properly when battered.
When an egg is broken onto a flat surface has a watery, spread-out white, this usually indicates that the egg is stale. The height of the albumin then is very important for the freshness of the egg, and it is measured as Haugh unit value. The highest the value, the fresher the egg is. It is known, when egg ages, the Haugh units value decrease and therefore the egg freshness is reduced. Haugh units comes from the height of the albumin adjusted by the size of the egg.
Therefore, any method or feeding practice that can increase or preserve the Haugh unit value, is considered highly beneficial for the egg industry.
A way has been discovered for reducing, if not eliminating, the need for refrigeration and spray oiling on eggs as a means of preserving interior egg quality.
To ameliorate the problem of interior egg degradation with time, the following procedures have been recommended heretofore:    1. Gather eggs three to four times per day.    2. Clean the eggs promptly after gathering and cool for 12-24 hours at 13° C. or preferably 10° C. before packing in cases or cartons.    3. Keep the eggs at between 60 to 85%, preferably 70 to 80%, relative humidity.    4. Resort to careful handling.    5. Use proper packing using precooled containers only.    6. Resort to frequent marketing of not less than twice a week.    7. Use speedy, refrigerated transportation and make frequent deliveries to sales outlets, preferably at least five times per week.    8. Use adequately refrigerated holding spaces at sales outlets.    9. Keep the eggs in home refrigerators at 7° C. to 13° C., and preferably use all of the eggs within one week.
The demand for poultry eggs, especially chicken eggs expanded considerably over the last decade. The poultry industry has grown from a home industry to a large scale manufacturing industry in which tens of thousands of eggs are produced daily at single farms or egg laying installations. Some eggs are produced for eating and some eggs are produced for hatching. One problem with such large scale egg producing is premature reduction in interior egg quality as a function of time. That is, unless eggs are handled and/or treated in accordance with the above 9-point program, their quality as regards internal qualities of the albumen and yolk may deteriorate faster than would be desired. Moreover, a way of simplifying egg production, distribution, marketing, etc. with concomitant reduction in refrigeration requirements would be a welcome contribution to the art.
Another problem associated with large scale egg production is breakage. Even a slight crack in an egg makes it unsuitable for hatching and most other marketing purposes. It is estimated that some six percent of all eggs produced are lost for marketing because of cracking or breakage. Shell strength is very important to inhibit breakage. The stronger the egg shell, the less likely the egg will be cracked or broken. Machinery and techniques necessary for carefully handling the eggs to avoid breakage are expensive and time consuming.
Another substantial loss of egg production, estimated to be about a seven percent loss, is the production of shell-less eggs. Any reduction in shell-less eggs can be an important factor in large scale egg production.
Another important measurement is the strength of the vitelline membrane. Very often the bakery, pasta and in general the egg products industry has to separate the egg from the white, in order to prepare different dishes and formulas. This is one of the most important quality criteria for the industrial egg sector. Therefore, when possible a strong and resistant egg yolk will be always preferable.